For example, 20090421xxxxxx, etc. Isn't this format YYYYMMDDHHMMSS?
Yes. It is a UTC date stamp.
<logger>
<TH date=20090403162928 id=th3 temp=17.0 hum=81 dew=13.7>
</logger>
That an example just grabbed from my Meteohub. Local time is 17:29 on 3rd April 2009.
The time stamp is 16:29 and 28 second UTC on 3rd April 2009.
So if your timestamp is correct it is showing 21st April!

WD should only be asking for data from before "now".
If the clock was wrong on the WD computer and it asked for "future" data I'd normally expect Meteohub to respond that it was a future time/date (unless of course its clock was wrong too).
You can generate a sample like the above, showing the "latest" sensor reading on the Meteohub using a url like this in a browser:
http://192.168.0.78/meteolog.cgi?mode=data&type=xmlJust replace 192.168.0.78 with the IP of your Meteohub.
The downloads will run until WD shuts down as described. Another thing I notice is that the download repeats itself. The same dates are being downloaded everytime I start WD. I have the correct date and time set on both Meteohub and the weather station.
I suggest checking the value in the [Davis Download] section of WDISPLAY.INI
That sets the time and date (in local time) that WD starts looking from when it starts up. When you have just shut WD down from a normal running state it ought to be set to within a minute of when you shut down.
I might also metion that I am using two copies of WD on the same computer. They are on different drives and have different folder names.
Multiple copies should not be a problem as such. I used to do that (with one connected to a WMR200, the other connected to Meteohub) before moving fully to Meteohub.
If the above doesn't give clues that lead to a solution, a copy & paste from
WD => View => WS2010-13/WS2500 data logger setup/info saved as a text file and attached to a message might help with diagnosis.
N.B. Grabbing the text to the clipboard can be tricky. [Ctrl][A] doesn't seem to work, so what I do is [RightClick][Select All] then [Crtl][C]. As soon as WD writes text to the wind the Select All is lost so you might need to try several times before you grab a goo copy.